A cohort of anti-HIV positive donors and controls has been under prospective follow-up since 1985. The original analysis of the study was published in the New England Journal of Medicine (321:917, 1989). A reanalysis of the data, six years after study initiation is in progress. At enrollment, 182 subjects were Western blot (WB) positive, including 158 asymptomatic donors, nine sexual partners of these donors and 15 persons HIV infected by blood transfusion. In addition, we enrolled a control population consisting of 70 donors who were anti-HIV reactive on the screening enzyme immunoassay (EIA), but WB negative or WB indeterminate (21). Of the 182 participants who were Western blot positive, 87% were donors, 5% sexual partners, and 8% recipients. Thus far, 28 patients (15%) were followed in the study until their deaths from AIDS; 12 (6.6%) additional patients developed AIDS and then left the study so that their mortality status is not currently known to the investigators. Seventeen patients under active follow-up also have AIDS. The total number of known AIDS cases is thus 57 or 31% of the WB+ cohort. In addition, there are 55 patients who have been lost to follow-up and whose AIDS and mortality status is unknown. We are trying to track these persons at the present time. Sixty-seven patients are in active follow-up with no evidence of AIDS, but varying degrees of CD4 lymphopenia. AIDS of HIV related phenomena have not developed in any of 21 WB indeterminate of WB negative subjects.